Combined information display and information input device

ABSTRACT

A combined information display and information input device comprising a matrix of independently addressable light emitting devices and a plurality of light sensing devices, the light emitting devices comprising organic light emitting diodes comprising organic light emitting material positioned between a low work function electrode and a high work function electrode characterized in that the light sensing devices comprise organic photovoltaic devices comprising at least an organic electron donor and at least an organic electron acceptor positioned between a high work function electrode and a low work function electrode. The combined information display and information input device has application as a touch screen, for example for a mobile communication device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device, which enables both thedisplay of information and the input of information. The device combineslight emitting elements to provide an information display function andlight sensing elements to provide an information-input function. Inparticular the invention relates to a combined information display andinformation input device based on organic materials wherein an organiclight emitting material is used to provide the light emitting functionand an organic light sensing material Is used to provide the lightsensing function. Methods of manufacture of such devices are also thesubject of the present invention.

2. Brief Description of the Prior Art

Apparatus capable of both displaying information and allowing the inputof information are known with the most well established technologiesoperating by means of a touch sensitive panel or film applied over thesurface of a standard display such as a backlit LCD or a CRT display.Such displays have the disadvantage that the introduction of a furthercomponent beyond those of the display itself adds to the complexity ofmanufacturing. In addition wear caused to the touch panel by regularcontact limits the durability of this component and contact with thesurface of the screen may cause distortion of the image displayed.

A number of efforts have been directed at integrating informationdisplay and information input functions onto a single substrate andthereby simplifying the manufacture of the displays. To date most ofthese efforts have been directed at the combination of LCD technologyand inorganic semiconductor photosensor technology. The advantage ofusing photosensors rather than touch sensors is that no contact with thescreen Is needed to input information.

The 1990's saw the growth of a display technology based on organic lightemitting materials. Light emitting devices based on organic lightemitting materials fall into two broad classes, those based on polymericlight emitting materials, as disclosed in WO90/13148, and those devicesbased on low molecular weight light emitting materials, so called smallmolecules, such as disclosed in U.S. Pat. No. 4,530,507. At around thesame time it was appreciated that the same semiconductive organicmaterials which provide the light emitting material in organic lightemitting devices could also be used to detect light, see in particularthe disclosure of the light sensing properties of light emittingpolymers in U.S. Pat. No. 5,331,183 and U.S. Pat. No. 5,523,555.

It has been proposed to use this dual operating function of lightemitting polymers to provide a device capable of both the display andthe input of information. U.S. Pat. No. 5,929,845 discloses a scannerbased on a matrix of organic light emitting devices with the devicesemitting light onto the surface of the image to be scanned, lightreflected from this image is detected by the display allowinginformation about the scanned image to be stored in a suitableinformation storage means and if desired displayed by means of thematrix of light emitting devices. This scanner device comprises a singlematrix of light emitting polymer devices with each device functioning asboth a light emitter and a light detector. U.S. Pat. No. 5,504,323 alsosuggests using a single matrix of organic light emitting devices witheach device acting as both light emitter and light detector. GB2315594discloses a scanning device where organic light emitting devices areused to provide a light source, light from which is reflected from theimage to be scanned, this reflected light is detected by light emittingpolymer based sensors.

In these prior art displays the organic electronic devices are used toprovide both a light emitting function, when forward biased, and a lightdetecting function, when reverse biased. The disadvantage of such anarrangement is that the organic electronic devices cannot be optimisedto perform both functions therefore any improvement in the light sensingproperty of the device will generally be detrimental to the lightemitting property of the device and vice versa. Such devices can thennot operate optimally as both right emitting devices and light sensingdevices. Further the need to operate the organic electronic devicesalternately in two modes requires complex electronic driving circuitry.

SUMMARY OF THE INVENTION

The inventors of the present application have developed a combinedinformation display and information input device which overcomes theproblems of the prior art displays. The combined information display andinformation input device of the present invention combines efficientlight emitting devices and efficient light sensing devices providing adevice which can be optimised for both the display of information andthe input of information. The light emitting devices and light sensingdevices of the present invention can be optimised independently, thisallows for the development of displays with better signal to noiseratios and displays which can, for example, display video images whilststill retaining a light sensing function.

Although the light emitting and light sensing devices can be optimisedseparately the similarity in the structures of the light emitting andlight sensing devices of the present invention allows the displays ofthe present invention to be manufactured using a relatively limitednumber of steps. Taking the similarities in structure of the lightemitting and light sensing devices of the present invention into accountthe inventors of the present application have developed an efficient andflexible method for the production of such devices. Further the presentinvention provides a range of device architectures and driving schemes.

In a first embodiment the present invention provides a combinedinformation display and information input device comprising a matrix ofindependently addressable light emitting devices and a plurality oflight sensing devices, said light emitting devices comprising organiclight emitting diodes comprising organic light emitting materialpositioned between a low work function electrode and a high workfunction electrode characterised in that said light sensing devicescomprise organic photovoltaic devices comprising at least an organicelectron donor and at least an organic electron acceptor positionedbetween a high work function electrode and a low work functionelectrode.

The light sensing, organic photovoltaic devices preferably comprise asemiconductive organic polymer as either the electron donor or electronacceptor, in a more preferred embodiment both electron donor andelectron acceptor are semiconductive organic polymers. The termselectron donor and electron acceptor are used in the art to describe theorganic materials used in an organic photovoltaic device, with electrondonor referring to materials having a low electron affinity and/or a lowionisation potential and electron acceptor referring to materials havinga high electron affinity and/or a high ionisation potential.

Examples of suitable organic semiconductive polymers includepolyfluorene, polybenzothiazole, polytriarylamine,poly(phenylenevinylene) and polythlophene. Polymers may be present as alayered structure or more preferably as a blend. In an alternativeembodiment the light sensing organic photovoltaic device may comprise afullerene, in particular devices comprising a blend of a fullerene and asemiconductive organic polymer are preferred. The organic photovoltaicdevice may comprise further additives such as molecular antenna whichenhance light absorption by the device. Porphyrins and phthalocyaninesare examples of molecular antenna.

The organic photovoltaic device comprises a high work functionelectrode, preferably having a work function of greater than 4.3 eV. Thehigh work function electrode provides for the collection of holes(positive charge carriers) from the layer of organic photovoltaicmaterial. Indium tin oxide is a preferred high work function electrodematerial. In order to increase the built in field formed across thephotovoltaic material by the high and low work function electrodes it ispreferred to provide a layer of hole transporting material between thehigh work function electrode and the organic photovoltaic material. Thehole transporting material is preferably polystyrene sulfonic acid dopedpolyethylene dioxythiophene, known as PEDOT:PSS.

The organic photovoltaic device comprises a low work function electrode,preferably having a work function of less than 3.5 eV. The low workfunction electrode provides for the collection of electrons (negativecharge carriers) into the layer of organic photovoltaic material.Preferred materials for forming the low work function electrode includeMg, Ca, Ba and Al. In order to increase the built in field formed acrossthe photovoltaic material by the high and low work function electrodesit is preferred to provide a layer of insulating material positionedbetween said layer of organic photovoltaic material and said low workfunction electrode. The layer of insulating material should besufficiently thin such that it allows charge collection into the lowwork function electrode from the layer of organic photovoltaic material,preferably the layer of insulating material has a thickness of between 1and 10 nm. Preferred materials for the layer of insulating materialinclude alkali or alkaline earth metal fluorides, such as UF or BaF₂.

The organic light emitting device comprises a high work functionelectrode, preferably having a work function of greater than 4.3 eV. Thehigh work function electrode provides for the injection of holes(positive charge carriers) into the layer of organic light emittingmaterial. Indium tin oxide is a preferred high work function electrodematerial. In order to further facilitate the injection of holes into thelayer of organic light emitting material it is preferred to provide alayer of hole transporting material between the high work functionelectrode and the organic light emitting material. The hole transportingmaterial is preferably polystyrene sulfonic add doped polyethylenedioxythlophene, known as PEDOT:PSS.

The organic light emitting device comprises a low work functionelectrode, preferably having a work function of less than 3.5 eV. Thelow work function electrode provides for the injection of electrons(negative charge carriers) into the layer of organic light emittingmaterial. Preferred materials for forming the low work functionelectrode include Mg, Ca, Ba and Al. In order to further facilitate theinjection of electrons into the layer of organic light emitting materialit is preferred to provide a layer of insulating material positionedbetween said layer of organic light emitting material and said low workfunction electrode. The layer of insulating material should besufficiently thin such that it allows charge injection from the low workfunction electrode into the layer of organic light emitting material,preferably the layer of insulating material has a thickness of between 1and 10 nm. Preferred material for the layer of insulating materialinclude alkali or alkaline earth metal fluorides, such as LiF or BaF₂.

The organic light emitting devices preferably comprises a semiconductiveorganic polymer as the light emitting material. The light emittingorganic semiconductive polymer is preferably selected from the groupcomprising polyfluorene, polybenzothiazole, polytriarylamine,poly(phenylenevinylene) and polythlophene. In a particularlyadvantageous embodiment the present invention provides a combinedinformation display and information input device wherein said organicphotovoltaic devices are sensitive to light in a non-visible region ofthe electromagnetic spectrum. Preferably the light sensing devices aresensitive to light in the infrared region of the electromagneticspectrum i.e. light having a wavelength greater than 700 nm.

The present invention is also directed to multicolour informationdisplays wherein said organic light emitting devices comprise a firstgroup of organic light emitting devices and a second group of organiclight emitting devices, said first group of organic light emittingdevices emitting light of a first colour and said second group of saidorganic light emitting devices emitting light of a second colour.Preferably the device comprises a third group of light emitting devicesemitting light of a third colour. The first second and third colours aremost preferably selected from amongst red, green and blue.

The present invention is further directed to displays emitting light ina non-visible region of the electromagnetic spectrum wherein saidorganic light emitting devices comprise both a group of light emittingdevices emitting light of a colour in the visible range of theelectromagnetic spectrum and a group of light emitting devices emittinglight in a non visible region of the electromagnetic spectrum.Preferably light emitted in a non-visible region of the electromagneticspectrum is emitted as light in the infrared region of theelectromagnetic spectrum i.e. light of a wavelength greater than 700 nm.

The combined information display and information input device comprisesa matrix of independently addressable light emitting devices. Preferablythis matrix comprises a plurality of light emitting device addressingcolumn electrodes and a plurality of light emitting device addressingrow electrodes with the organic light emitting devices being positionedat the intersection of said column electrodes and said row electrodes.The row and column electrodes will preferably have an orthogonalarrangement relative to each other. The row and column electrodes may beformed by a strip of conducting material placed in electrical contactwith the high work function electrode of the organic light emittingdevice and a strip of conducting material in electrical contact with thelow work function electrode of the organic light emitting device.Alternatively the row and column electrodes may be formed by the highwork function electrodes of the light emitting devices being formed asstrips of high work function electrode material connecting neighboringlight emitting devices and the low work function electrodes of the lightemitting devices being formed as strips of low work function materialconnecting neighbouring light emitting devices. It is preferred that therow addressing electrodes are formed from or in contact with the highwork function electrode of the light emitting devices and that thecolumn addressing electrodes are formed from or are in contact with thelow work function electrodes of the light emitting devices.

In a particularly preferred embodiment the plurality of light sensingdevices comprises a matrix of independently addressable light sensingdevices. Preferably this matrix comprises a plurality of light sensingdevice addressing column electrodes and a plurality of light sensingdevice addressing row electrodes with the organic photovoltaic devicesbeing positioned at the intersection of said column electrodes and saidrow electrodes. The row and column electrodes will preferably have anorthogonal arrangement relative to each other. The row and columnelectrodes may be formed by a strip of conducting material placed inelectrical contact with the high work function electrode of the organicphotovoltaic device and a strip of conducting material in contact withthe low work function electrode of the organic photovoltaic device.Alternatively the row and column electrodes may be formed by the highwork function electrodes of the organic photovoltaic devices beingformed as strips of high work function electrode material connectingneighbouring organic photovoltaic devices and the low work functionelectrodes of the organic photovoltaic devices being formed as strips oflow work function material connecting neighbouring organic photovoltaicdevices. It is preferred that the row addressing electrodes are formedfrom or in contact with the high work function electrode of the lightemitting devices and that the column addressing electrodes are formedfrom or are in contact with the low work function electrodes of thelight emitting devices.

The combined information display and information input device preferablyfurther comprises a combined column driver and detector for addressingsaid light emitting device column electrodes and said light sensingdevice column electrodes. The column driver and detector comprisingcircuitry for providing a forward bias to said light emitting devices tocause them to emit light and comprising circuitry for detecting lightincident on said light sensing devices. In an alternative embodimentseparate column drivers are provided for addressing the columnelectrodes of the light emitting devices and the light sensing devicesand in such an embodiment the device comprises a) a column driver foraddressing said light emitting device column electrodes said columndriver comprising circuitry for providing a forward bias to said lightemitting devices to cause them to emit light and comprising b) a columndetector for addressing said light sensing device column electrodes,said column detector comprising circuitry for detecting light incidenton said light sensing devices. The column detector may further comprisecircuitry for reverse biasing the photovoltaic devices.

The combined information display and information input device mayfurther comprise a combined row selector driver for addressing saidlight emitting device row electrodes and said light sensing device rowelectrodes. In an alternative embodiment separate row selectors areprovided for addressing the light emitting device row electrodes and thelight sensing device row electrodes, in such an embodiment the devicecomprises a) a light emitting device row selector driver for addressingsaid light emitting devices row electrodes and b) a light sensing devicerow selector driver for addressing said light sensing device rowelectrodes.

Preferably in devices comprising a combined column driver and detectoror a separate column detector, the column detector further comprises ameans for reverse biasing the light sensing devices. Reverse biasing oforganic photovoltaic devices has been shown to increase theirsensitivity to incident light.

A suitable method for driving the combined displays of the presentinvention involves applying a regular scanning signal to the rowelectrodes, addressing each row electrode in turn, whilst supplying asignal to the column electrodes of the light emitting devices from whichlight emission is required. In a similar manner a scanning signal may beapplied to the row electrodes of the light sensing devices and thesignal generated by incident light at a given light sensing device maybe read at the column electrode. In such a method it is preferred to usea dock signal generating means for applying the scanning signal to therow electrodes. The role of the dock signal generating means is toprovide a scanning signal to the combined row selector driver or to boththe light emitting device row selector driver and the light sensingdevice row selector driver according to whether the light emitting andlight sensing devices are addressed by a single set of row electrodes orby two separate sets of row electrodes.

It is preferred that the dock signal generating means provides scanningsignals to the combined row selector driver or to said light emittingdevice row selector driver and said light sensing device row selectordriver at a first higher frequency and a second lower frequency. Thefirst higher frequency scanning signal addressing the light emittingdevice row electrodes and the second lower frequency scanning signaladdressing the light sensing device row electrodes. In this manner thelight emitting devices are addressed more frequently than the lightsensing devices.

In a particular embodiment two clock signal generating means may be usedto apply signals to the row electrodes, with a first clock signalgenerating means providing a scanning signal to the light emittingdevice row electrodes and a second dock signal generating meansproviding a scanning signal to the light sensing device row electrodes.It is preferred that the first clock signal generating means provides ahigher frequency scanning signal than the second clock signal generatingmeans.

The present invention is also directed to a method for preparing acombined information display and information input device by means ofselectively depositing the organic materials which constitute the lightemitting and light sensing devices onto a patterned substrate.Accordingly the present invention is directed to a method of preparing acombined information display and information input device comprising;

a) providing a substrate,

b) providing a patterned layer of conducting material having a high workfunction,

c) providing a patterned layer of organic light emitting material and apatterned layer of organic photovoltaic material said organicphotovoltaic material comprising at least an organic electron donor andat least an organic electron acceptor,

d) providing a layer of a conducting material having a low workfunction.

The organic light emitting material and the organic photovoltaicmaterial may be deposited either simultaneously or sequentially ineither order.

It is preferred that said layer of conducting material of low workfunction is provided as a patterned layer of conductive material of lowwork function. A patterned layer of hole transporting material may alsobe provided over said layer of conductive material of high workfunction.

It is preferred that at least one of said steps of providing a patternedlayer of organic light emitting material, providing a patterned layer oforganic photovoltaic material or patterned layer of hole transportingmaterial over said layer of conductive material of high work functioncomprises applying said material using a method of selective printing.Methods of selective printing include ink-jet printing, flexographicprinting, gravure printing or screen printing. In particular inkjetprinting is the preferred selective printing method.

A particularly preferred method of preparing a combined informationdisplay and information input device involves the steps of;

a) providing a substrate,

b) providing a patterned layer of conducting material having a high workfunction,

c) providing a first layer of insulating material over said layer ofconducting material said first layer of insulating material beingpatterned to form a series of wells,

d) providing a second layer of insulating material said second layer ofinsulating material being patterned to form a series of parallel banksover said first layer of insulating material,

e) optionally depositing by means of ink-jet printing a layer of holetransporting material into a selection of said wells,

f) depositing by means of inkjet printing a layer of an organic lightemitting material into a first selection of said wells,

g) depositing by means of ink-jet printing a layer of organicphotovoltaic material comprising at least an organic electron donor andat least an organic electron acceptor into a second selection of saidwells,

h) depositing a layer of a conducting material having a low workfunction over said layer of organic light emitting material and saidlayer of organic photovoltaic material, wherein steps f) and g) may becarried out in any order.

The present invention also provides a method for preparing a combinedinformation display and information input device where rows of lightemitting devices and rows of light sensing devices are addressed byseparate row electrodes. This method comprises;

a) providing a substrate,

b) providing a patterned layer of conducting material having a high workfunction,

c) providing a first layer of insulating material over said layer ofconducting material said first layer of insulating material beingpatterned to form a series of wells,

d) providing a second layer of insulating material, said second layer ofinsulating material being patterned to form a series of parallel banksover said first layer of insulating material,

e) optionally depositing by means of inkjet printing a layer of holetransporting material into a selection of said wells,

f) depositing by means of inkjet printing a third layer of insulatingmaterial in a first selection of said wells,

g) depositing by means of ink-jet printing a layer of an organic lightemitting material into a second selection of said wells,

h) depositing by means of ink-jet printing a layer of organicphotovoltaic material comprising at least an organic electron donor andat least an organic electron acceptor into a third selection of saidwells,

i) depositing a layer of a conducting material having a low workfunction over said layer of organic light emitting material and saidlayer of organic photovoltaic material, wherein steps e), f), g) or h)may be carried out in any order provided that when present the layer ofhole transporting material is deposited prior to the deposition of theorganic light emitting material or the organic photovoltaic material. inthe above mentioned methods the first and second layers of insulatingmaterials are preferably photopatternable polymers. The third layer ofinsulating material is preferably a soluble insulating material suitablefor deposition by selective printing techniques such as ink-jetprinting.

The present invention is further directed to the use of a combinedinformation display and information input device according to thepresent invention as a touch screen and further to the use of a combinedinformation display and information input device according to thepresent invention as an image scanner. The present invention is furtherdirected to a mobile communication device comprising a combinedinformation display and information input device according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a) shows a first mode of operation of a combined informationdisplay and information input device.

FIG. 1 b) shows a second mode of operation of a combined informationdisplay and information input device.

FIG. 2 a) shows a mode of operation of a combined information displayand information input device wherein an infrared light emitting pointingdevice is used to input information to the display.

FIG. 2 b) shows a mode of operation of a combined information displayand information input device wherein light emitted by an infraredemitting pixel is reflected to an infrared detecting pixel by a pointingdevice.

FIG. 3 shows in cross section a typical device structure of a combinedinformation display and information input device.

FIG. 4 a) to g) shows a method of manufacture of an information displayand information input device where light emitting pixels and lightsensing pixels are addressed by the same row electrodes.

FIG. 5 a) to d) shows a method of manufacture of an information displayand information input device where light emitting pixels and lightsensing pixels are addressed by the different row electrodes.

FIG. 6 a) shows an implementation of a combined information display andinformation input device using a single column driver/detector and asingle row selector to address the light emitting and light sensingpixels.

FIG. 6 b) shows a typical pixel layout for the implementation of FIG. 6a).

FIG. 7 a) shows an implementation of a combined information display andinformation input device using a column driver, a separate columndetector and a single row selector to address the light emitting andlight sensing pixels.

FIG. 7 b) shows a typical pixel layout for the implementation of FIG. 7a).

FIG. 8 a) shows an implementation of a combined information display andinformation input device using a column driver, a column detector and apair of row selectors to address the light emitting and light sensingpixels.

FIG. 8 b) shows a typical pixel layout for the implementation of FIG. 8a).

DESCRIPTION OF PREFERRED EMBODIMENTS

The combined information display and information input device of thepresent invention has a matrix of light emitting devices, also known aspixels, which can be turned on or off to display an image. The displayalso has a set of light sensing devices, these are organic photovoltaicdevices which are herein referred to as photodetector pixels. Thephotodetector pixels are distributed over the display and provide ameans of detecting light intensity incident on the display surface. Thelight intensity distribution on the display's surface will be modulatedby, for example, approaching a pointing device toward the screen. Inthis manner a user may input information into the display device. Thepointing device may act to decrease light intensity at a point on thesurface of the display by casting a shadow over certain of thephotodetector pixels or may act to increase light intensity at a pointon the surface of the display by reflecting light emitted from thedisplay pixels back toward the photodetector pixels. The light intensityat each photodetector pixel may then be read to yield information on thespatial location of the pointing device on the display surface, thelocation will be detectable as either an increase or decrease in lightintensity at a particular location on the display surface.

FIG. 1 a) shows schematically an array of light emitting pixels 101 andphotodetector pixels 102 on a substrate 100. Pointing device 103 shieldsone or more of the photodetector pixels 104 from ambient light, this ismeasured as a decrease in light intensity at photodetector pixel 104 andallows the position of the pointer to be established. Alternatively, asshown in FIG. 1 b) perturbations in light intensity may be determined bymeasuring the increase in light intensity at a particular location onthe display surface. Here an array of light emitting pixels 112 andphotodetector pixels 111 are arranged on a substrate 110. A pointingdevice 113 placed in proximity to the display surface reflects lightemitted by the light emitting pixels back towards the display surface,this causes an increase in light intensity at the photodetector 114 inproximity to the pointing device. It is apparent that by using adistribution of photodetector pixels across the display, such as a x-yarray of photodetector pixels, a map of light intensity over the surfaceof the display may be established, allowing the location of a pointerdevice to be established. Comparison of the distribution of lightintensity over the display surface at different points in time willallow the movement of a pointer device across the surface of the displayto be monitored. Perturbations in light intensity over the surface ofthe display may be used to provide input to the display device such asby allowing a user to point to an Icon on the display or to input textinto the display by writing on the display surface.

In order to build up an image of the location of the perturbation oflight intensity due to the pointer it will be necessary to deconvolvethe perturbation in light intensity due to the pointer from fluctuationsand inhomogeneity in the ambient light falling on the display's surfaceand variation in the light emitted by the display due to the display ofa moving image. In order to simplify this procedure photodetector pixelsmay be tuned to detect light of a particular wavelength, in particularlight of a non-visible wavelength such as infrared light having awavelength of greater than 700 nm. Tuning of the photodetector pixelsmay be achieved by using a photodetector pixel comprising an organicmaterial which is inherently more sensitive to light in the desiredregion of the electromagnetic spectrum or by using a filter to removelight of wavelengths other than those desired. Using a pointing deviceemitting light at the wavelength to which the photodetector pixel istuned will then allow the signal detected at the photodetector pixelsdue to the pointer to be readily distinguished from perturbations due toambient light and light emitted by the display pixels. FIG. 2 a) showsthe mode of operation of such a device, an array of light emittingpixels 201 and photodetector pixels 202 which are more sensitive tolight in a non-visible region of the electromagnetic spectrum arearranged on a surface 200, a pointer device 203 which emits light in theregion of the electromagnetic spectrum at which photodetector pixels 202are sensitive is used to input information into the display.

An alternative to using a light emitting pointing device is to providelight emitting devices on the display surface which emit light in anon-visible region of the electromagnetic spectrum and using the pointerto reflect this light back to the photodetector pixels which are tunedto detect light at this wavelength. FIG. 2 b) illustrates this mode ofoperation wherein an array of light emitting devices emitting light inthe visible region of the electromagnetic spectrum 212, an array oflight emitting devices emitting light in a non-visible region of theelectromagnetic spectrum 211 and an array of photodetector pixelssensitive to light in a non-visible region of the electromagneticspectrum 213 are arranged on a substrate 210. Pointer 214 causes lightemitted from the display surface to be reflected back towards thedisplay causing an increase in light intensity to be measured at thephotodetector pixels. The photodetector pixels only detect light in theselected non-visible region of the electromagnetic spectrum so thefunctioning of the light detecting element of the display is notaffected by fluctuations in incident light or changes in visible lightemitted by the display due to the display of, for example, a movingimage.

Another method to simplify the detection of the perturbation of lightintensity due to the pointer is to use a lock in frequency amplifierwhereby light at a particular frequency is emitted from the pointer orfrom the light emitting pixels of the display and the photodetectorpixels are operated to act as phase sensitive detectors such that onlylight having this particular frequency is detected. Detection of lightintensity by the photodetector pixels will not then be affected bychanges in ambient light or changes in the image displayed on thedisplay.

In order to build up an image of the perturbation of light intensity onthe display surface due to the movement of a pointing device it isnecessary that the photodetector pixels are distributed across thesurface of the display. The photodetector pixels may be present in theform of a x-y matrix. Clearly the more photodetector pixels present onthe display surface the greater the sensitivity of the input function ofthe display although the pitch of the photodetector pixels may notnecessarily be as fine as the pitch of the light emitting pixels. Todisplay a high-resolution image it is necessary that the light emittingpixels of the display occupy as much of the display surface as possibletherefore it is preferable that the resolution of the photodetectorpixels is lower than that of the light emitting pixels.

FIG. 3 shows the typical structure of a light emitting pixel 300 and aphotodetector pixel 310 according to the present invention. For clarityFIG. 3 shows the two pixels to be of the same size and proximate to eachother, clearly in a practical device the two types of pixel may be ofdifferent size and may be distributed such that, for example, thedisplay has only a single photodetector pixel for every three or morelight emitting pixels. The display comprises a substrate 301, suitablesubstrates include glass, ceramics and plastics such as acrylic resins,polycarbonate resins, polyester resins, polyethylene terephthalateresins and cyclic olefin resins. The substrate may be transparent,semi-transparent or, in cases where light is to be emitted and detectedfrom the opposite side of the device, opaque. The substrate may be rigidor flexible and may comprise a composite material such as, for example,the glass and plastic composite disclosed in EP0949850.

The substrate 301 is coated with a layer of conductive material of highwork function 302 to form the anode of the eventual light-emitting andlight detecting devices. Where it is desired that light be emittedthrough the substrate this conductive material should be transparent orsemi-transparent and is selected from materials having a work functiongreater than 4.3 eV, such as indium-tin oxide (ITO), tin oxide, aluminumor indium doped zinc oxide, magnesium-indium oxide, cadmium tin-oxide,gold, sliver, nickel, palladium and platinum. ITO is the preferred highwork function material. The high work function material is generallypatterned to form an addressing element of the eventual matrix of lightemitting devices. The pattern preferably is in the form of a series ofparallel lines. These lines are typically of thickness of severalhundreds of microns with gaps of several tens of microns between theparallel lines.

The light emitting pixel 300 comprises a layer of hole transportingmaterial 304. Suitable hole transporting materials include polystyrenesulfonic acid doped polyethylene dioxythlophene (PEDOT:PSS), asdisclosed in WO98/05187, polyaniline or TPD(N,N′-diphenyl-N,N′-bis(3-methylphenyl)[1,1′-biphenyl]4,4′-diamine).Over the layer of hole transporting material is a layer of lightemitting material 305. The light emitting material may be a polymericlight emitting material, such as disclosed in Bernius et al AdvancedMaterials, 2000, 12, 1737 or a low molecular weight light emittingmaterial such aluminum trisquinoline, as disclosed in U.S. Pat. No.5,294,869. The light emitting material may comprise a blend of a lightemitting material and a fluorescent dye or may comprise a layeredstructure of a light emitting material and a fluorescent dye. Lightemitting polymers include polyfluorene, polybenzothlazole,polytriarylamine, poly(phenylenevinylene) and polythophene. Preferredlight emitting polymers include homopolymers and copolymers of9,9-di-n-octylfluorene (F8), N,N-bis(phenyl)-4-sec-butylphenylamine(TFB) and benzothiadiazole (BT). A layer of electron transporting orhole blocking material may be positioned over the layer of lightemitting material if required to improve device efficiency.

A layer of material of low work function 306, which serves as a cathode,is positioned over the layer of light emitting material. Examples ofsuitable materials for the cathode include Li, Na, K, Rb, Be, Mg, Ca,Sr, Ba, Yb, Sm and Al. The cathode may comprise an alloy of such metalsor an alloy of such metals in combination with other metals, for examplethe alloys MgAg and LiAl. The cathode preferably comprises multiplelayers, for example Ca/Al or LiA/Al. The device may further comprise alayer of dielectric material between the cathode and the emitting layer,such as is disclosed in WO 97/42666. In particular it is preferred touse an alkali or alkaline earth metal fluoride as a dielectric layerbetween the cathode and the emitting material. Preferred cathodestructures include LIF/Ca/Al and BaF₂/Ca/Al. In some cases it may bedesired that the cathode be transparent, for example when an opaquesubstrate or anode is used or where it is desired that the whole devicebe transparent. Suitable transparent cathodes include a cathodecomprising a thin layer of highly conductive material such as Ca and athicker layer of transparent conducting material such as ITO, apreferred transparent cathode structure comprises BaFa₂/Ca/Au.

The mode of operation of the light emitting device is summarised asfollows. A potential difference is provided between the anode 302 andthe cathode 306, this results in the injection of charge carriers fromthe electrodes into the layer of light emitting material 305. Positivecharge carriers or holes are injected from the anode and negative chargecarriers are injected from the cathode. The two types of charge carriercombine in the layer of light emitting material to form an exciton whichdecays emitting a photon.

The light sensing device 310 is an organic photovoltaic device known asan organic heterojunction device, such devices are disclosed in U.S.Pat. No. 5,454,880. A typical organic heterojunction photovoltaic devicecomprises a layer of high work function material 302 on a substrate 301.Since the present display comprises a combination of light emittingdevices and light detecting devices it is most practical to provide bothtypes of devices on a single substrate and to address both types ofdevices using a single conductive material of high work function.Therefore the description of suitable materials for the substrate andhigh work function material of the light emitting device also apply tothose of the light detecting device.

The photovoltaic device 310 comprises a layer of hole transportingmaterial 312. Suitable hole transporting materials include polystyrenesulfonic acid doped polyethylene dioxythiophene (PEDOT:PSS), asdisclosed in WO98/05187, polyaniline or TPD(N,N′-diphenyl-N,N′-bis(3-methylphenyl)[1,1′-biphenyl]4,4′-diamine).Over the layer of hole transporting material is provided a layer oforganic photovoltaic material 313. The organic photovoltaic materialcomprises an electron donor and an electron acceptor.

A variety of structures of the organic photovoltaic devices arepossible. The electron donor and electron acceptor may comprise polymersor low molecular weight compounds. The electron donor and acceptor maybe present as two separate layers, as disclosed in WO99/49525, or as ablend, as disclosed in U.S. Pat. No. 5,670,791, a so called bulkheterojunction. The electron donor and acceptor may be selected fromperylene derivatives such as N,N′-diphenylglyoxaline-3,4,9,10-perylenetetracarboxylic acid diacidamide, fullerenes (C₆₀), fullerenederivatives and fullerene containing polymers and semiconducting organicpolymers such as polyfuorenes, polybenzothiazoles, polytriarylamines,poly(phenylenevinylenes), polyphenylenes, polythiophenes, polypyrroles,polyacetylenes, polylsonaphthalenes and polyquinolines. Preferredpolymers include MEH-PPV (poly(2-methoxy,5-(2′-ethyl)hexyloxy-p-phenylenevinylene)), MEHCN-PPV(poly(2,5-bis(nitrilemethyl)-1-methoxy-4-(2′-ethyl-hexyloxy)benzene-co-2,5-dialdehyde-I-methoxy4-(2′-ethylhexyloxy)benzene))and CN-PPV cyano substituted PPV, polyalkylthiophenes, such aspoly(3-hexylthiophene), POPT poly(3(4-octylphenyl)thiophene) andpoly(3-dodecyithlophene), polyfluorenes, such aspoly(2,7-9,9-dinotylfluorene),poly(2,7-(9,9-di-n-octylfluoreneybenzothiadiazole) andpoly(2,7-(9,9-di-n-octylfluorene)-(4,7-di-2-thienylfbenzothiazole)).Typical device structures include a blend ofN,N′-diphenylglyoxaline-3,4,9,10-perylene tetracarboxylic adddiacidamide and poly(3-dodecylthiophene), dodecylthiophene), a layeredstructure comprising a layer of MEH-PPV and a layer of C₆₀, a blend ofMEH-PPV and C₆₀, a layered structure comprising a layer of MEH-CN-PPVand a layer of POPT, a blend comprising MEH-PPV and CN-PPV and a blendcomprising poly(3-hexylthiophene) andpoly(2,7-(9,9-di-n-octylfluorene)-(4,7-di-2-thienyl-(benzothiazole)). Acathode 314 of material of low work function is provided over the layerof organic photovoltaic material. Materials suitable for the cathode ofthe light emitting device are also suitable for the cathode of thephotovoltaic device.

Organic heterojunction photovoltaic devices operate in the mannerdescribed as follows. The electrodes of different work function set upan internal electric field across the device. Absorption of light by thematerials of the organic layer generates bound electron-hole pairs,termed exitons. Excitons generated on the material of lower electronaffinity dissociate by transfer of an electron to the material of higherelectron affinity, the material of lower electron affinity is sometimesreferred to as the electron donor or simply donor. Excitons generated onthe material of higher electron affinity dissociate by transfer of ahole to the material of lower electron affinity, the material of higherelectron affinity is sometimes referred to as the electron acceptor orsimply acceptor. The electrons and holes generated by dissociation ofthe exictons then move through the device, with electrons moving to thelower work function cathode and holes moving to the higher work functionanode. In this way light incident on the device generates a currentwhich may be used in an external circuit. In the devices of the presentinvention the current generated at the photovoltaic device is measuredusing suitable circuitry and this provides a measurement of the lightintensity incident on the photovoltaic device. In this way thephotovoltaic device can be considered to operate as a photodetector,detecting light inddent on the device. Applying an additional potentialdifference between the electrodes of the organic photodetector increasesits sensitivity by increasing charge carrier mobility, improving chargetransport and reducing charge carrier recombination.

The display device comprising the organic light emitting devices andorganic photodetector devices may also be provided with an encapsulantwhich acts to seal the device from the atmosphere. Suitable methods ofencapsulation include covering the device on the cathode side with ametal can or glass sheet or providing an impermeable film over thedevice, such as a film comprising a stack of polymer layers andinorganic layers.

The performance of the device may be enhanced by adding optical elementsto improve light extraction from the light emitting pixels and toimprove light input into the photodetector pixels. Methods of enhancinglight extraction include the provision of microcavities and materials oflow dielectric constant over the surface of the light emitting pixelthrough which light is emitting. Methods of improving light input intothe photodetector pixels include the provision of antireflection films,microlenses or a corrugated surface over the surface of thephotodetector pixel.

The substrate and the patterned layer of high work function material maybe prepared using techniques known in the art, for example sputterdeposition of ITO followed by photolithographic patterning. The holetransporting material may be deposited by a number of techniques knownin the art and may be patterned or unpatterned. Typical methods ofdeposition of the hole transport material include vapour deposition,dose spaced deposition, laser induced thermal transfer, spin coating,doctor blade coating or selective printing. Selective printing methodsare preferred as they do not require complex and expensive equipment,such as vacuum chambers, and give a high degree of control over theresolution of the pattern obtained. Selective printing techniquesinclude screen printing, flexographic printing, gravure printing andink-jet printing. Of these techniques ink-jet printing is preferred asthis technique offers a high degree of resolution and a greater controlover the location of the pixels and the thickness of the device layersof the pixels.

The light emitting material and the electron donor and electron acceptorwhich comprise the photovoltaic material may be deposited by a suitablepatterning technique. Both soluble and insoluble organic materials maybe deposited by techniques such as vapour deposition, close spaceddeposition and laser induced thermal transfer. Soluble organicmaterials, such as light emitting polymers, may be deposited byselective printing methods such as screen printing, flexographicprinting, gravure printing and inklet printing. These techniques may beused to build multiple layers of organic materials. As discussed aboveinkjet printing is the preferred method of patterning.

The low work function material which forms the upper electrode orcathode of the devices is generally deposited by vapour deposition,although a suitable material may be printed. In most cases the cathodewill be patterned, this is achieved by vapour depositing the cathodematerial through a shadow mask, a particularly advantageous techniqueinvolves depositing the cathode through an integral shadow mask asexplained below.

The similarity in device structure of the organic light emitting deviceand the organic photodetector is an advantage of the combinedinformation display and information input device of the presentinvention. The two devices share a number of features such as the natureof the electrodes and the use of a hole transporting layer. Thesesimilarities allow the devices to be prepared in a very efficient mannerwith a limited number of steps and with the same manufacturing stepsbeing carried out to form both the light emitting devices and thephotodetectors. In the combined information display and informationinput devices of the prior art, such as a combination of LCDs andsemiconductor photodetectors, the display function and the lightdetection function are provided by devices which are substantiallydifferent in structure and so the production of these devices requires agreater number of steps.

A significant advantage of the device of the present invention is thatthe preferred organic materials which constitute the device, inparticular conducting and semiconducting polymers, are soluble and canbe deposited using solution deposition techniques and in particularprinting techniques. Printing techniques do not require expensive andcomplex equipment, are potentially environmentally benign and may beapplied to a great range of substrates such as flexible substrates. Thefollowing gives a detailed description of the use of ink jet printing toprepare devices according to the present invention comprising lightemitting and light detecting materials based on polymers. Clearly otherselective printing methods such as flexographic printing could also beused.

FIG. 4 illustrates a preferred method of preparing a combinedinformation display and information input device 400 according to thepresent invention. FIG. 4(a) shows a cross sectional view of a glasssubstrate 401 suitable for a device of the present invention. Thesubstrate is coated with a layer of ITO 402 to form the anode of theeventual organic electronic devices. ITO may be deposited by sputteringor any other suitable method known to those in the art The ITO layer onthe substrate is then patterned using photolithography, wherein thelayer of ITO is coated with a photoresist, patterned, for example usinga UV source and a photomask, and developed using the appropriatedeveloping solution, exposed ITO is then removed by chemical etching,leaving a patterned layer of ITO. Typically the ITO is patterned to forma series of parallel stripes.

A layer of photopatternable, insulating polymer such as a polyimide or afluorinated photoresist 403 is then deposited onto the patterned ITO asshown in FIG. 4(b). The photopatternable polymer may be deposited byspin-coating, doctor blade coating or any other suitable technique. Thephotopatternable polymer is patterned using conventionalphotolithographic techniques, for example after deposition thephotopatternable polymer is dried, exposed to UV light through a mask,soft baked, developed using, for example, tetramethylammonium hydroxide,rinsed and hard baked. Preferred patterns of the insulating polymer arethose that define banks, which are one dimensional patterns, for exampleparallel stripes, or wells, which are two dimensional patterns ofrecesses in the insulating polymer. Banks typically have a height of 0.5to 10 microns and a width of 10 to 100 microns and define channelscontaining regions of ITO having a width of 10 to 500 microns. Wells mayhave a diameter of 10 to 100 microns. FIG. 4 b) shows a substrate 401with a patterned layer of ITO 402 and a layer of photopatternablepolymer 403 which has been patterned to form a series of wells. One ofthe functions of the wells is to define the pixel areas of the eventuallight emitting and light detecting devices.

The substrate is then provided with a further layer of photopatternablepolymer 404 as shown in FIG. 4 c). This layer of photopatternablepolymer is patterned to form a series of parallel banks running in adirection orthogonal to the patterned lines of ITO. The second layer ofphotopatternable polymer is patterned using similar methods to thefirst. It is advantageous if the photopatternable polymer 404 is etchedso as to leave banks having an negative wall profile as illustrated inFIG. 4(c). Banks 404 having a negative wall profile are narrower inproximity to the substrate, typically a bank will have an upper width ofaround 40 microns and a lower width of around 20 to 38 microns.Techniques for obtaining banks with a negative wall profile are known inthe art and, in the case of a negative photoresist, involveunderexposing and then overdeveloping the photoresist. The provision ofbanks with a negative wail profile is beneficial for the furtherprocessing of the substrate, in particular banks having a negative wallprofile aid the patterned deposition of the metallic cathode. EP0969701discloses the use of banks having a negative wall profile in thedeposition of a cathode in an organic electroluminescent device. Wherethe first layer of photopatternable polymer 403,comprises a pattern ofwells these generally have a positive wall profile, this enables anydeposited solution to flow more easily into the well. Techniques forobtaining wells with a positive wall profile are known in the art andtypically, in the case of a negative photoresist, involve overexposingand then underdeveloping the photoresist

The substrate, layers of photopatternable polymer and exposed ITO may befurther surface treated for example using oxygen plasma or ultravioletlight. This serves to alter the surface energies of the materials of thesubstrate making them more suitable for the deposition of the devicelayers. Surface treatment is particularly desirable when furthermaterials are to be deposited by solution processing techniques.

A layer of hole-transporting material, FIG. 4 d) 405, is then depositedupon the patterned ITO. The preferred hole-transport material used inthe art is a conductive organic polymer such as polystyrene sulfonicacid doped polyethylene dioxythlophene (PEDOT:PSS) as disclosed inWO98/05187, although other hole transporting materials such as dopedpolyaniline may also be used. The hole-transporting material may bedeposited by spin coating. The hole transporting material is preferablydeposited by ink jet printing. PEDOT:PSS may be inkjet printed as anaqueous solution.

Following deposition of the hole transporting layer, a layer of lightemitting material, FIG. 4 e) 406 is deposited into selected wells on thesubstrate. To form a monochrome display with a ratio of 1:1 between thenumber of light emitting pixel to the number of photodetector pixels thelight emitting material is deposited in alternate wells. To form an RGBdisplay with a ratio of 3:1 between the number of light emitting pixelsand the number of photodetector pixels light emitting material isdeposited in three out of every four wells with red, green and bluelight emitting materials being deposited as appropriate. A wide range ofother distributions are possible, for example a 9:1 ratio of lightemitting to photodetecting pixels. Alternatively a material emittinglight in a non-visible region of the electromagnetic spectrum may bedeposited in addition to the material of the light emitting pixels.Light emitting polymer is deposited using ink-jet printing. Conjugatedpolymers such as polyfluorene and poly(phenylene vinylene) may beink-Jet printed from solutions of aromatic solvents such as toluene,xylene, trimethylbenzene etc.

Following deposition of the light emitting material on selected pixelsthe organic photovoltaic material is deposited in all, or a selectionof, the remaining pixels, FIG. 4 f) 407. Ink-jet printing is thepreferred method for the deposition of the photovoltaic material. Theorganic photovoltaic material may be deposited as a blend or may bedeposited in two steps to form a layered structure. Where the organicphotovoltaic material comprises a conjugated polymer this may be ink-jetprinted using an aromatic solvent such as toluene, xylene, mesitylene ortrimethylbenzene.

The printing strategy used to deposit the organic light emittingmaterial and the organic photovoltaic material may be varied. Forexample the organic light emitting material may be deposited in a firstpass of the ink-jet printing head or heads and the organic photovoltaicmaterial may be deposited in a second pass of the inkjet printing heador heads, or vice-versa. Alternatively the organic light emittingmaterial and the organic photovoltaic material may be deposited duringthe same pass of the inklet printing heads or heads.

A cathode material 408 is then deposited over the light emittingmaterial and the light detecting material. The cathode material isdeposited by means of vapour deposition. Where appropriate multilayercathodes may be deposited, for example the cathodes comprising a layerof alkali or alkaline earth metal fluorides and layers of metals asdiscussed above. A particularly preferred cathode comprises UF/Ca/Al,with a layer of LIF of thickness from 1 to 10 nm, a layer of Ca ofthickness of 1 to 25 nm and a layer of Al of thickness 10 to 500 nm. Itis a notable advantage of the present invention that a single cathodemay be deposited over both the light emitting devices and thephotovoltaic devices without the need for carrying out multistep metaldeposition processes.

The device is then encapsulated, this may be carried out by means ofenclosing the device in a metal can or glass cover to protect the devicefrom the environment, an oxygen or moisture absorbent may be includingwithin the metal can or glass cover, such a technique is disclosed inU.S. Pat. No. 6,080,031. Alternatively devices may be encapsulated bylaminating an impermeable composite material over the device as isdisclosed in WO00/36661. Given the similarity in structure of the lightemitting devices and photovoltaic devices of the present invention thesame encapsulation system may be used to protect both types of devicefrom the environment since the different devices are likely to besusceptible to similar environmental degradation mechanisms.

In a particularly preferred embodiment the combined information displayand information input device is prepared such that the light emittingdevices and the photodetectors are on separate rows of the display. Thisis in contrast to the device shown in FIG. 4 where light emittingdevices and photodetectors are provided on the same row of the display.The advantages of this arrangement will become apparent later in thedescription and relate to the benefits of electrically insulatingneighbouring light emitting and photodetector pixels.

FIG. 5 a) shows schematically a section of a combined informationdisplay and information input device 500. The display comprises a matrixof light emitting pixels of different colours, namely red 503, green504, and blue 505, and photodetectors 506 arranged in rows and columns.The light emitting pixels and photodetector pixels are positioned onseparate rows and columns with for example light emitting devicessituation on row 501 and photodetectors on row 502. Pixels on the row oflight emitting devices which correspond to the position of thephotodetector pixels on the row of light sensing devices are filled withan insulating material 507. Likewise pixels on the row of light sensingdevices which correspond to the position of the light emitting pixels onthe row of light emitting devices are filled with an insulatingmaterial. The insulating material serves to prevent contact between thecathodes and anodes which run along the rows and columns and therebyprevent any electrical shorting at what would otherwise be vacantpixels. Clearly other arrangements of light emitting devices andphotodetectors are possible, for example whereby one row ofphotodetector pixels is present for every nine rows of light emittingpixels.

Displays corresponding to FIG. 5 a) are prepared in the followingmanner. FIGS. 5 b) to 6 d) show the preparation of a row of lightemitting pixels 510 e.g. FIG. 5 b)i) and the preparation of a row ofphotodetector pixels 520 e.g. FIG. 5 b)ii). The display substrate isprepared as outlined above to provide a substrate 511, 521, a patternedlayer of high work function conductive material such as ITO 512, 522, alayer of photopatternable insulating material patterned to form a matrixof wells 513, 523 and a layer of photopatternable insulating materialpatterned to form a series of parallel banks 514, 524. Pixels in the rowof light emitting devices FIG. 5 b)i) which correspond to photodetectorpixels in the row of photodetectors are filled with an insulatingmaterial 515, likewise pixels in the row of photodetectors FIG. 5 b)ii)which correspond to light emitting pixels in the row of light emittingdevices are filled with an insulating material 525. The insulatingmaterial may be any suitable insulating material and is preferablypolymethylmethacrylate, polyvinylphenol or polystyrene. The insulatingmaterial may be deposited by any suitable method, but it is preferredthat the insulating material is deposited by a selective printingprocess and most preferably by means of ink jet printing. For thisreason it is preferred to use insulating materials such as polystyrenewhich are soluble in aromatic solvents such as toluene and xylene.

Following the deposition of the insulating material 515, 525 the lightemitting and photodetector devices may be prepared in the mannerdescribed above. A layer of hole transporting material such as PEDOT:PSSis provided over the exposed regions of high work function material,FIG. 5 c) i) and 11) 516, 526. A layer of light emitting material isdeposited into the pixels which will form the light emitting devices,FIG. 5 d)i) shows a device with a layers of red 517, green 518 and blue519 materials. A layer or several layers of organic photovoltaicmaterial 527 is deposited into the pixels which will form the eventuallight sensing devices FIG. 5 d)ii). Suitable methods of deposition ofthese materials are a outlined above but ink jet printing is a mostpreferred method. Finally a cathode is deposited and the device isencapsulated as described above (not shown).

The use of ink-jet printing to deposit the lightemitting andphotovoltaic materials of the pixels allows a great degree of variationin pixel layout to be achieved on a standard substrate. The density ofphotovoltaic pixels may be varied, for example with only one row ofphotovoltaic pixels for every nine rows of light emitting pixels, such apixel layout allows more of the surface area of the display to bededicated to. displaying information. To increase the sensitivity of thelight detecting function of the display larger photovoltaic pixels maybe used.

The light emitting pixels of the combined information display andinformation input device of the present invention are arranged in theform of a matrix of independently addressable light emitting devices.Typically this matrix will comprise a series of light emitting deviceaddressing column electrodes and a series of light emitting deviceaddressing row electrodes with the light emitting devices positioned atthe intersection of the row and column electrodes. Generally the columnand row electrodes will have an orthogonal arrangement relative to eachother. Although the row and column electrodes may be formed on thecathode and anode of the light emitting devices using a separateconductive layer, it is preferred that the anode and cathode of thelight emitting device are themselves used to form the row and columnelectrodes respectively. In such an embodiment the anode will be formedas a continuous strip on the substrate and will serve to connectadjacent devices and the cathode will be formed as a continuous stripover the layer of light emitting material also connecting adjacentdevices, with the cathode and anode in an orthogonal arrangement.Generally the row addressing electrodes will be formed from or incontact with the anode or high work function electrode and the columnaddressing electrodes will be formed from or in contact with the cathodeor low work function electrode. The matrix of light emitting deviceswill typically have a resolution of 100-200 pixels per inch.

The light sensing devices may also be present as a matrix ofindependently addressable photodetector pixels. Alternative embodimentsmay be envisaged where, for example, photodetector pixels aredistributed unevenly across the surface of the display, having a greaterconcentration in regions of the display which are commonly used todisplay information for a greater proportion of the time, such as thecentral portion of the display area. The matrix of photodetector pixelswill be similar to the matrix of light emitting devices whereby thematrix is formed from an orthogonal arrangement of row and columnelectrodes with the photodetector pixels situated at the intersectionsof the row and column electrodes, preferably the row and columnelectrodes will be formed from the electrodes of the photodetectoritself. The matrix of photodetectors will typically have a lowerresolution than the matrix of light emitting pixels.

The matrices of light emitting and photodetector pixels may be addressedeither passively or actively. In a passive matrix the light emittingpixels are arranged in a simple grid of rows and columns with chargebeing driven along a particular column or row and another row or columnbeing grounded, the pixel at the intersection of the selected row andcolumn emits light. Photodetector pixels may be addressed in a similarmanner with charge being detected on a particular row or column ratherthan being driven along it. Generally charge will be driven or detectedon a column whilst the rows will be sequentially grounded to scan thedisplay. In an active matrix a switch generally a transistor, and astorage means; generally a capacitor, are located at each pixel. As inpassive matrix addressing individual light emitting pixels are addressedby means of row and column electrodes with a particular row beingswitched on and a charge being sent down a column. This charge is storedon a storage means located at the pixel and discharges through the lightemitting device causing emission of light. In the case of photodetectorpixels the pixels are addressed in the same manner using the appropriaterow and column but rather than driving charge onto the pixel the chargeat the pixel generated by incident light is read out by appropriatecircuitry, which is generally situated on the column electrode.

A photodetector pixel may also comprise a capacitor, or other chargestorage means, for the storage of the charge built up at the pixelduring a given addressing period. Such an arrangement allows integrationof the signal and increases sensitivity.

The electronic driving of such a matrix of light emitting and lightsensing devices is now described with particular reference to thedriving of passive matrix arrays, clearly similar arrangements could beapplied to the driving of active matrix arrays. The arrangementcomprises a column driver for providing current to the light emittingdevices to cause them to emit light, a column detector for detecting thecurrent or voltage generated at the photodetector due to incident lightand a row selector for scanning the now electrodes of the light emittingdevices and the photodetectors. There is further a central processorunit for providing video or other image data to the column driver, forreceiving the input from the column detector and for providing thetiming signal to the row electrodes. Various arrangements of the columndriver, column detector and the row selector are possible.

FIG. 6 a) shows an implementation of a combined information display andinformation input device 600 using a single column driver/detector 601and a single row selector 602 to address the light emitting 603 andlight sensing pixels 604. Processor 605 provides a scanning signal tothe row electrodes 606 whereby each row electrode is addressed insequence. In order to provide a video signal the rows are scanned at afrequency of around 50 Hz. Processor 605 inputs a video, text or othersignal to the column driver 601 which in turn provides a correspondingelectrical signal to the appropriate column electrodes 607 of the lightemitting pixels. Column detector 601 comprises circuitry for detectingthe electrical signal at the photodetectors generated due to incidentlight. This signal forms the information input provided to the processor605. The column driver circuitry provides a forward bias voltage to thelight emitting pixels causing them to emit light. The column detectorcircuitry, in addition to containing circuitry for detecting the chargegenerated at a particular pixel may also comprise circuitry for reversebiasing the photodetector pixels to increase their sensitivity to light.

FIG. 6 b) shows a typical pixel layout for the implementation of thedriving scheme of FIG. 6 a). In this case the display is an RGB or fullcolour display having red 603 a, green 603 b and blue 603 c pixels witha photodetector pixel 604. The light emitting pixels and thephotodetector pixels are addressed by separate column electrodes 607 andby the same row electrode 606.

FIG. 6 a) shows a single column driver/detector being used to addressboth the column electrodes of the light emitting devices and the columnelectrodes of the photodetectors. However, rather than provide a singledriver to perform the two functions of inputting information to bedisplayed to the light emitting pixels and reading out the informationinput at the photodetector pixels it would also be possible to provide aseparate driver for providing the display signal input to the lightemitting pixels and a separate detector to read out the information fromthe photodetector pixels. Such an arrangement is shown in FIG. 7 a).FIG. 7 a) shows a combined information display and information inputdevice 700 comprising a driver 701 addressing the column electrodes 709of the light emitting pixels 705, a detector 702 addressing the columnelectrodes 708 of the photodetector pixels 704. A row selector 703addresses the rows of light emitting pixels and photodetector pixels707. A processor 706 provides a clock signal to the row selector 703,provides video, text or other signal to the column driver 701 and readsout information from the detector circuitry 702. FIG. 7 b) shows atypical pixel layout for such an embodiment with three light emittingpixels 705 a, 705 b and 705 c a photodetector pixel 704, columnelectrodes addressing the light emitting pixels 709 and columnelectrodes addressing, the photodetector pixels 708. The light emittingpixels and the photodetectors are addressed by a single row electrode707.

To cause sufficient light emission from the light emitting pixelsrequires a relatively large current, typically 1 mA. Such a largecurrent causes considerable leakage onto neighbouring light emittingpixels and photodetector pixels. Since the current generated by incidentlight at a photodetector pixel is relatively small in some cases it mayprove difficult to distinguish the current generated at a photodetectorpixel due to incident light from the leakage current from neighbouringlight emitting pixels. The drive scheme of FIG. 8 a) in which the lightemitting pixels and the photodetector pixels are addressed by separaterow electrodes overcomes the problem of leakage current. FIG. 8 a) showsa combined information display and information input device 800comprising a driver 801 addressing the column electrodes 810 of thelight emitting pixels 806, a detector 802 addressing the columnelectrodes 809 of the photodetectors 805. A light emitting pixel rowselector 804 addressing the row electrodes 807 of the light emittingpixels 806 and a photodetector row selector 803 addressing the rowelectrodes 808 of the photodetector pixels 805. A processor 811 providesa scanning signal to the light emitting pixel row selector 804, ascanning signal to the photodetector row selector 803, a video, text orother signal to the column driver 801 and reads out information from thedetector circuitry 802.

FIG. 8 b) illustrates a typical pixel configuration for the drivingembodiment of FIG. 8 a). A series of RGB light emitting pixels 806 a,806 b and 806 c are addressed by light emitting device column electrodes810 and light emitting device row electrodes 807. Photodetector pixels805 are addressed by a series of photodetector addressing columnelectrodes 809 and a series of photodetector row electrodes 808.Positions 812 along the light emitting device row electrodes whichcorrespond to photodetectors on the photodetector row electrodes arefilled with insulating material to prevent contact between the row andcolumn electrodes at these sites. Likewise positions along thephotodetector row electrodes which correspond to light emitting pixelson the light emitting device row electrodes are filled with insulatingmaterial 813. Such pixel layout schemes prevent cross talk or leakagebetween the light emitting pixels and the photodetectors and thereforeincreases the sensitivity of the light input function of the combinedinformation display and information input device. A method for preparingsuch a pixel layout is described above, see FIG. 5. As mentioned abovethe decrease in the resolution of the photodetector pixels when usingsuch a pixel arrangement is not necessarily disadvantageous since theresolution of the photodetector pixels is not required to be as high asthe resolution of the light emitting pixels.

The processor of the above described embodiments carries out a number offunctions including providing display information to the driver andreading out information from the photodetectors via the detectorcircuitry. The processor also provides a scanning signal to the rowelectrodes. This is carried out using a dock signal generating meanswhich provides a regular signal causing the row selector to switch fromaddressing one of the row electrodes to another of the row electrodes.This sequence typically involves scanning neighbouring row electrodessequentially although other sequences are possible, for example scanningevery other row electrode or scanning only every fourth row electrode.The frequency of scanning is adjusted according to the information to bedisplayed, for example the display of video information requires the rowelectrodes to be scanned at a frequency of 50 Hz. The photodetectorpixels do not require scanning at such a high frequency since such arate of change in the information input to the photodetector pixels isunlikely. For this reason it is preferred that the processor either hasa single clock signal generating means able to provide clock signals atleast two different frequencies or that the processor has two clocksignal generating means, providing clock signals at differentfrequencies. The higher of the two frequencies is used to scan the lightemitting device row electrodes and the lower of the two frequencies isused to scan the photodetector row electrodes. In embodiments such asthat of FIG. 8 where the light emitting devices and the photodetectorsare situated on separate rows the different frequency scanning signalscan be provided to each row selector separately. In embodiments wherethe light emitting devices and the photodetectors are situated on thesame row, such as in FIGS. 6 and 7, the display may be scanned at afirst higher frequency and information input to the driver from theprocessor to cause information to be displayed and the display may bescanned at a lower frequency with information being read out from thedetector. For example the light emitting pixels may be driven at afrequency of 50 Hz and the photodetectors may be read at a frequency of2 Hz, therefore on every 25^(th) cycle of the row selector informationwill be read out of the detector circuitry with the light emittingdevices being driven for the other 24 cycles. A further advantage ofthis driving scheme is that the current generated on the photodetectormay be stored on a capacitor or other storage means until thephotodetector is addressed, allowing a signal of greater magnitude to begenerated at each photodetector and so requiring less sensitive currentdetecting circuitry in the detector.

The above described information display and information input device mayserve a number of functions. For example, as a touch screen where a usermay respond to information displayed on the device by pointing at thedevice with a finger, stylus or other means with the information inputfunction of the device then reading the information input by the user.The user may input information by for example pointing to an Icon on thescreen or writing on the screen. Such a touch screen could be used in atablet PC, PDA, mobile phone, ATM, games console etc. The informationdisplay and information input device of the present invention isparticularly suited to applications in mobile computing since in thesame surface area the device provides both a relatively large areadisplay and a relatively large area input device with suitable softwareallowing the user to switch between the two functions or combinations ofthe two functions as appropriate.

The information display and information input device may also be used asa scanner. In this mode the device operates in a manner similar to aconventional scanner. A document is placed on the device, the lightemitting devices provide a light source which is reflected from thedocument and the photodetectors convert the intensity of the reflectedlight into a signal which is read out by the processor via the detectorcircuitry. Filters may be used to allow the photodetectors todistinguish light of different colours or the organic material of thephotodetector may be selected such that it is more sensitive to light ofa particular wavelength with photodetectors sensitive to each of red,green and blue being provided in the scanner. Alternatively aphotodetector pixel able to detect over a broad range of wavelengths maybe used with the red, green and blue light emitting pixels used togenerate colour information about the image being scanned.

EXAMPLE

The following example describes the preparation of a combined lightemitting and light sensing device wherein the light emitting pixels andphotodetector pixels are situated on different row electrodes.

A glass substrate coated with ITO patterned to form parallel lines ofthickness 270 microns with gaps of 30 microns between the lines isprovided. A layer of polyimide (Brewer Polyin T15010) is then spincoated onto the substrate. The polyimide is patterned to form a matrixof wells having a diameter of 75 microns. Following formation of thewells the substrate is coated with a further layer of polyimide. Thesecond layer of polyimide is patterned to form parallel banks having aheight of 10 microns and a width of 40 microns, leaving a channel ofexposed ITO between the banks and wells having a width of 260 microns.The substrate comprises an array of 160 by 120 pixels.

The ITO and photoresist coated substrate is then exposed to an O₂/CF₄plasma treatment. The plasma treatment is carried out in a RF barreletcher of dimensions 300 mm diameter, 450 mm depth, with a gas mixtureof 0.52% CF₄ in oxygen, at a pressure of 1.5 Torr and a power of 400 W.

A layer of PEDOT:PSS comprising a 0.5% aqueous solution (available fromBayer as Baytron P) is then ink-jet printed onto the wells of thesubstrate forming a layer of thickness 50 nm over the exposed regions ofITO (suitable inkjet printers are available from Litrex, USA). ThePEDOT:PSS formulation is printed into alternate wells along each columnof light emitting pixels and into alternate wells along each column ofphotodetector pixels. An insulator is then deposited into the emptywells i.e. Into the wells which do not contain PEDOT:PSS. The insulatorcomprises polystyrene which is ink-jet printed from a 0.5% toluenesolution.

To form the light emitting pixels a layer of a polyfluorene, a copolymerof F8, TFB and BT which emits green light, is inkjet printed onto thePEDOT:PSS layer from a 1.5% solution in xylene:trimethylbenzene solvent,forming a layer of polyfluorene of thickness 100 nm over the PEDOT:PSS.The light emitting polyfuorene is deposited sequentially into pixelscontaining a layer of PEDOT:PSS in alternate rows of the device.

Photodetector pixels are prepared by ink-jet printing a blend ofpoly(3-hexylthiophene) andpoly(2,7-(9,9-di-n-octylfluorene)-(4,7-di-2-thienyl-(benzothiazole)) ina 1% solution in xylene over the layer of PEDOT:PSS to form a layer ofphotovoltaic material of 100 nm thickness. Photodetector pixels areformed by printing into wells which contain a layer of PEDOT:PSS onalternate rows of the device. Photodetector pixels are formed onalternate pixels along the row such that no column contains both aphotodetector pixel and a light emitting pixel.

A cathode comprising a layer of calcium of thickness 50 nm and a layerof aluminum of thickness 250 nm is then deposited upon the pixels bymeans of vacuum deposition. Devices are encapsulated using a metal canand UV curable adhesive.

No doubt the teaching herein makes many other embodiments of, andeffective alternatives to, the present invention apparent to a personskilled in the art. The present invention is not limited to the specificembodiments described herein but encompasses modifications which wouldbe apparent to those skilled in the art and lying with the spirit andscope of the attached claims.

1.-56. (canceled)
 57. A combined information display and informationinput device comprising a matrix of independently addressable lightemitting devices and a plurality of light sensing devices, said lightemitting devices comprising organic light emitting diodes comprisingorganic light emitting material positioned between a low work functionelectrode and a high work function electrode wherein said light sensingdevices comprise organic photovoltaic devices comprising at least anorganic electron donor and at least an organic electron acceptorpositioned between a high work function electrode and a low workfunction electrode.
 58. The device of claim 57 wherein at least one ofsaid organic electron donor and said organic electron acceptor comprisesa semiconductive organic polymer.
 59. The device of claim 57 wherein atleast one of said organic electron donor and said organic electronacceptor comprises a fullerene.
 60. The device of claim 57 wherein saidorganic electron donor and said organic electron acceptor comprisesemiconductive organic polymers.
 61. The device of claim 57 wherein saidorganic electron donor and said organic electron acceptor comprise ablend of semiconductive organic electron donor polymer andsemiconductive organic electron acceptor polymer.
 62. The device ofclaim 57 wherein at least one of said organic photovoltaic devices issensitive to light in a non-visible region of the electromagneticspectrum.
 63. The device of claim 57 wherein more than one of saidorganic photovoltaic devices are sensitive to light in a non-visibleregion of the electromagnetic spectrum.
 64. The device of claim 57wherein all of said organic photovoltaic devices are sensitive to lightin a non-visible region of the electromagnetic spectrum.
 65. The deviceof claim 57 wherein at least one of said organic photovoltaic devices issensitive to light in the infrared region of the electromagneticspectrum.
 66. The device of claim 57 wherein more than one of saidorganic photovoltaic devices are sensitive to light in the infraredregion of the electromagnetic spectrum.
 67. The device of claim 57wherein all of said photovoltaic devices are sensitive to light in theinfrared region of the electromagnetic spectrum.
 68. The device of claim57 wherein said organic light emitting devices comprise a group of lightemitting devices emitting light of a color in the visible range of theelectromagnetic spectrum and a further group of light emitting devicesemitting light in a non-visible region of the electromagnetic spectrum.69. The device of claim 68 wherein said further group of light emittingdevices emit light in the infrared region of the electromagneticspectrum.
 70. The device of claim 57 wherein said matrix ofindependently addressable light emitting devices comprises a pluralityof light emitting device addressing column electrodes and a plurality oflight emitting device addressing row electrodes, said column electrodesintersecting said row electrodes, and said organic light emittingdevices being positioned at the intersection of said column electrodesand said row electrodes.
 71. The device of claim 70 wherein saidplurality of light sensing devices comprises a matrix of independentlyaddressable light sensing devices.
 72. The device of claim 71 whereinsaid matrix of independently addressable light sensing devices comprisesa plurality of light sensing device addressing column electrodes and aplurality of light sensing device addressing row electrodes, said columnelectrodes intersecting said row electrodes, and said light sensingdevices being positioned at the intersection of said column electrodesand said row electrodes.
 73. The device of claim 72 further comprising acombined column driver and detector for addressing said light emittingdevice column electrodes and said light sensing device columnelectrodes, said column driver and detector comprising circuitry forproviding a forward bias to said light emitting devices to cause them toemit light and comprising circuitry for detecting light incident on saidlight sensing devices.
 74. The device of claim 72 comprising a) a columndriver for addressing said light emitting device column electrodes, saidcolumn driver comprising circuitry for providing a forward bias to saidlight emitting devices to cause them to emit light, and b) a columndetector for addressing said light sensing device column electrodes,said column detector comprising circuitry for detecting light incidenton said light sensing devices.
 75. The device of claim 72 furthercomprising a combined row selector driver for addressing said lightemitting device row electrodes and said light sensing device rowelectrodes.
 76. The device of claim 72 further comprising (a) a lightemitting device row selector driver for addressing said light emittingdevices row electrodes and (b) a light sensing device row selectordriver for addressing said light sensing device row electrodes.
 77. Thedevice of claim 73 wherein said combined column driver and detector orsaid column detector further comprises means for reverse biasing saidlight sensing devices.
 78. The device of claim 74 further comprising aclock signal generator for providing a scanning signal to the combinedrow selector driver or to said light emitting device row selector driverand said light sensing device row selector driver.
 79. The device ofclaim 78 wherein said clock signal generator provides scanning signalsto the combined row selector driver or to said light emitting device rowselector driver and said light sensing device row selector driver at afirst higher frequency and a second lower frequency said first higherfrequency scanning signal addressing said light emitting device rowelectrodes and said second lower frequency scanning signal addressingsaid light sensing device row electrodes.
 80. The device of claim 76further comprising a first clock signal generator and a second clocksignal generator, said first clock signal generator providing a scanningsignal to said light emitting device row electrodes and said secondclock signal generator providing a scanning signal to said light sensingdevice row electrodes.
 81. The device of claim 80 wherein said firstclock signal generator provides a higher frequency scanning signal thansaid second clock signal generator.
 82. Method of preparing a combinedinformation display and information input device comprising the stepsof: (a) providing a substrate, (b) providing a patterned layer ofconducting material having a high work function, (c) providing apatterned layer of organic light emitting material and a patterned layerof organic photovoltaic material, said organic photovoltaic materialcomprising at least an organic electron donor and at least an organicelectron acceptor, and (d) providing a layer of a conducting materialhaving a low work function, wherein at least one of said steps ofproviding a patterned layer of organic light emitting material or apatterned layer of organic photovoltaic material over said layer ofconductive material of high work function comprises applying saidmaterial using a method of selective printing.
 83. The method of claim82 wherein said method of selective printing is selected from the groupconsisting of ink-jet printing, flexographic printing, gravure printing,and screen printing.
 84. The method of claim 83 wherein said method ofselective printing comprises ink-jet printing.
 85. Method of preparing acombined information display and information input device according toclaim 1 comprising the steps of: (a) providing a substrate, (b)providing a patterned layer of conducting material having a high workfunction, (c) providing a first layer of insulating material over saidlayer of conducting material said first layer of insulating materialbeing patterned to form a series of wells, (d) providing a second layerof insulating material said second layer of insulating material beingpatterned to form a series of parallel banks over said first layer ofinsulating material, (e) optionally depositing by means of ink-jetprinting a layer of hole transporting material into a selection of saidwells, (f) depositing by means of ink-jet printing a layer of an organiclight emitting material into a first selection of said wells, (g)depositing by means of ink-jet printing a layer of organic photovoltaicmaterial comprising at least an organic electron donor and at least anorganic electron acceptor into a second selection of said wells, and (h)depositing a layer of a conducting material having a low work functionover said layer of organic light emitting material and said layer oforganic photovoltaic material, wherein steps (f) and (g) may be carriedout in any order.
 86. Method of preparing a combined information displayand information input device according-to claim 1, comprising the stepsof; (a) providing a substrate, (b) providing a patterned layer ofconducting material having a high work function, (c) providing a firstlayer of insulating material over said layer of conducting material saidfirst layer of insulating material being patterned to form a series ofwells, (d) providing a second layer of insulating material, said secondlayer of insulating material being patterned to form a series ofparallel banks over said first layer of insulating material, (e)optionally depositing by means of ink-jet printing a layer of holetransporting material into a selection of said wells, (f) depositing bymeans of ink-jet printing a third layer of insulating material in afirst selection of said wells, (g) depositing by means of ink-jetprinting a layer of an organic light emitting material into a secondselection of said wells, (h) depositing by means of ink-jet printing alayer of organic photovoltaic material comprising at least an organicelectron donor and at least an organic electron acceptor into a thirdselection of said wells, and (i) depositing a layer of a conductingmaterial having a low work function over said layer of organic lightemitting material and said layer of organic photovoltaic material,wherein steps (e), (f), (g) and (h) may be carried out in any orderprovided that when present the layer of hole transporting material isdeposited prior to the deposition of the organic light emitting materialor the organic photovoltaic material.